The lithium-ion battery market has been in a period of dynamic growth ever since Sony introduced the first commercial cell in 1991. The lithium-ion battery system has become increasingly popular in applications such as portable computers, camcorders and cellular phones. As new materials are developed, cost reduction should spur growth in new applications. Carbonaceous materials have been used as anode electrodes, thus avoiding the dendritic growth of metallic lithium upon charging, prolonging the cycle life of a whole cell and improving the reliability. On the other hand, a carbon anode may lower the specific energy density of a cell due to both a high reversible potential and a limited amount of lithium uptake in the carbon matrix. These two factors vary with the type of carbon material. Thus far, carbon materials such as natural graphite, cokes, carbon fibers, non-graphitizable carbon, and pyrolitic carbon have been investigated, but critical parameters such as surface area and porosity are difficult to predict and control for these materials.
Previously, disordered carbons with more predictable properties have been prepared using inorganic templates containing well-defined pore sizes, as reported in Journal. Electrochem. Society 1996, 143, L95 and Res. Soc. Symp. Proc., Macroporous and Microporous Materials 1996, 431, 39. The carbons have been tested in electrochemical cells as anodes in lithium secondary batteries. They deliver high specific capacity (a measure of the power in mAh/g) and display excellent performance in terms of the number of cycles runs, as reported in Journal New Mat. Electrochem. Systems 1998, 1, 83. Although the performance of the clay-derived carbons is excellent, there is still a need to improve the efficiency of the synthetic process without sacrificing electrochemical performance of the resulting carbons. We have discovered that using a particular clay called sepiolite as an inorganic template to load organic precursors has produced superior results. Sepiolite has fibers of 0.2 to 2 .mu.m in length, 100.times.300 .ANG. in width and a thickness of 50 to 100 .ANG.. The fibrous structure is composed of ribbons with two sheets of tetrahedral silica units, linked by oxygen atoms to a central octahedral sheet of magnesium so that the tetrahedral sheet of silicon is continuous, but with the directions of the apical extremes of the tetrahedral sheets of silica inverted after every six tetrahedral units. This spatial configuration determines the presence of channels oriented in the longitudinal direction of the fibers.